Demetrius Constantine Dounis (also Demetrios), also known as D. C. Dounis (Greek: Δημήτριος Κωνσταντίνος Δούνης; c.1886 to 1894 – August 13, 1954), was an influential teacher of violin and string instrument technique, as well as violinist, violist, and mandolin player.Considerable uncertainty prevails on the subject of Dounis's early life, beginning with the date of his birth in Athens, variously given as 1886 (according to most library catalogues), 1893, or 1894. He is said to have performed his first violin recital at the age of 7, and to have toured the United States as a mandolinist at 14. In Athens, he participated in the famous Athenian Mandolinata, conducted by Nikolaos Lavdas. He studied under František Ondříček in Vienna], where he also took a medical degree, specializing in neurology and psychiatry. He also studied in Paris with César Thomson. After World War I, when he served as a doctor in the Greek army, he was appointed to the chair in violin at the State Conservatory of Thessaloniki, but soon established himself in the United States.